Paper core crush or compression tester and method



Jan. 5, 1965 w. c. JONES 3,164,010

PAPER CORE CRUSH OR COMPRESSION TESTER AND METHOD Filed April 20, 1962 INVENTOR.

Wail/ c2222 C 'CfOJZQS BY 5% v.16 W W United States Patent 3,164,010 PAPER CORE CRUSH 0R CGMPRESSION TESTER AND METHOD William C. Jones, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed Apr. 20, 1962, Ser. No. 189,092 6 Claims. (Cl.-7394) This invention relates to a testing machine for determination of crush or compression resistance of paper cores, such as used for winding rolls of plastic film.

Frequently, when plastic film is wound upon a paper core, shrinkage of the film will occur and exert relatively high pressure on the core. In some instances, the pres sure may be sufiicient to cause collapse of the core. When the core is mounted upon a mandrel in a wrapping machine, compressive forces may be developed during film windup of such magnitude as to bind the core upon the mandrel.

The invention disclosed herein may be conveniently utilized for determination of crush or compressive resistance of paper cores used for winding rolls of plastic film. In the manufacture of paper cores it is important that they be thoroughly oven dried, if full strength is to be realized. The machine of the invention may be used to spot test a shipment of paper cores to determine if they meet specifications regarding compressive strength.

The main object of this invention is to provide a testing machine for determination of crush or compression resistance of paper cores.

Other objects are to provide a paper core testing machine Which is easy to use, of low cost, and which will give reliable results.

These and further objects and features of the invention will become more apparent from the following description and accompanying drawing wherein:

FIG. 1 is an elevation view of a core tester embodying the principles of the invention;

FIG. 2 is a view generally as seen along line 22 in FIG. 1; and

FIG. 3 is a development view of a strap used in the device of FIG. 1.

The core tester of the invention includes a table or stand 6, upon which is mounted a frame means comprising a pair of vertically arranged, rectangular uprights, or posts 8, the upper ends of which support a platform It). A tension gage is mounted on the platform, which gage includes a dial indicator 12 adapted to show tension force developed in the tester. A gripping means, in the form of a vise-type band mounting head 14, is affixed to a rod 16 which is connected to the tension gage. A similar type of band mounting head 18, is arranged in vertical spaced relation below the mounting head 14, the mounting head 18 being afiixed to a rod 20. The latter is secured to a head piece 22 which is attached to a horizontal cross arm 24, the ends of which are arranged for vertical movement in guide slots 26 formed in the posts 8.

A rod 28 afiixed to the cross arm 24, is movable vertically by a power transmission mechanism, such as a rack and gear assemblage 30, which may be manually powered by a hand wheel 32 secured to a shaft 34 of the assemblage. Other types of power transmissions, manual or otherwise, will of course suggest themselves, the type disclosed being merely for purpose of illustration.

A metal'strap or band 36, is connected by its ends to the mounting heads 14 and 18. The strap 36, is adapted to form a loop 38 around a core 40, which is to be tested. The lower end of the strap is arranged for passing through an opening in the form of a rectangular hole 42, formed in the strap. It will be seen that a pulling force on the strap, when wound upon a core 46 in the 3,164,010 Patented Jan. 5, 1965 manner shown, will cause the loop 38 to assume a reduced diameter.

When using the device of the invention to determine the compression resistance of a core, a slotted metal sleeve 43 is placed upon a core 40, and a metal cylindrical plug 44 is placed in the core, which plug is of such diameter as to provide a slip fit Within the core. The metal sleeve 43 reduces the friction between the strap 36 and the core to be tested. The diameter of the plug 44 is similar to that'of a mandrel upon which the core will be mounted in a film winding machine (not shsown) As the tension in the strap is increased by operation of the rack and gear assemblage 30, the core will be compressed upon the plug 44. After a given amount of tension is attained, an axially pushing force is applied to the plu 44. If the plug slides easily, greater tension is applied to the strap, and a further plug sliding test made. At some point in the testing, it will be found that the plug 44, will not be easily movable; this is the value, as shown by the dial indicator 12, which indicates the limit of compressive resistance of the core under test. In actual practice, a calibration curve or chart, is prepared which shows the compressive force upon a given core for any combination of core diameter, strap width, indicator reading, etc. In such manner the compressive resistance of any core may be determined, which is of great value, since it will indicate the amount of film windup tension the core will resist before binding upon its supporting mandrel in a film winding machine.

In utilizing the apparatus of the invention, it may be desirable to place a protecting screen, or shield about the apparatus as a safety measure for protection in event the strap 36 should break during test.

It will be seen that they invention, as above disclosed, will satisfy the objectives set forth hereinbefore.

The foregoing description has been given in detail without thought of limitation since the inventive principles involved are capable of assuming other forms without departing from the spirit of the invention or the scope of the following claims.

What is claimed is:

l. A device for testing the compressive resistance of cylindrical elements comprising in combination, a frame means, a pair of gripping means supported in spaced relation upon said frame means, a strap afiixed at each end to one of said gripping means, said strap being arranged to provide a loop which decreases in internal dimension as the ends of the strap are moved apart, a tension gage supported upon the frame and arranged for connection with the first of said gripping means, a power transmission mechanism supported upon the frame means and arranged for connection with the second of said gripping means to provide movement of the second gripping means relative to said first gripping means, and a compressible sleeve positionable in the loop of said strap, said sleeve having an internal diameter substantially equal to the external diameter of a cylindrical element to be tested in the device.

2. A device for testing the compressive strength of paper cores comprising in combination, a table, a frame means supported upon said table, ,a platform afiixed to the frame means, a tension gage supported upon the platform, a first gripping means connected to said tension gage, a power transmission means supported by said table, a second gripping means connected to said power trans mission means, said transmission means being operative to cause movement of said second gripping means relative to said first gripping means, a strap aflixed at each end to one of said gripping means, said strap being formed to provide a loop which decreases in internal dimension as the ends of the strap are moved apart, and a compressible sleeve positionable in the loop of said strap, said sleeve having an'internal diameter substantially equal to the externaldiameter of a cylindrical element to be tested in the device.

3. A device according to claim 2, wherein said power transmission means comprises a rack and gear, and a hand wheel for rotation of a shaft on which said gear is mounted,

4. A device according to claim 2 wherein said strap is formed to provide an opening therein for passage therethrough of one end portion of the strap.

5. A device according to claim 2, wherein a cylindrical plug is provided for placementin a core positioned in said loop in readiness for testing.

6. A method for testing the compression resistance a of a paper core including the steps of, placing a cylindrical element in the core, which element is manually slidable Within the core, applying uniform magnitude radially directed forces upon the exterior surface of the core, continuing application of such forces until the cylindrical element will no longer be manually slidable within the core, and registering the magnitude of the radial forces at the no-slide condition of the cylindrical element.

References Cited in the file of this patent UNITED STATES PATENTS 477,043 (Ihadbourne et al June 14, 1892 813,033 Bellamy Feb. 20, 1906 1,332,570 Ray Mar. 2, 1920 1,662,648 Wasson Mar. 13, 1928 1,929,837 Cathcard Oct. 10, 1933 2,493,233 Dower Jan. 3, 1950 

1. A DEVICE FOR TESTING THE COMPRESSIVE RESISTANCE OF CYLINDRICAL ELEMENTS COMPRISING IN COMBINATION, A FRAME MEANS, A PAIR OF GRIPPING MEANS SUPPORTED IN SPACED RELATION UPON SAID FRAME MEANS, A STRAP AFFIXED AT EACH END TO ONE OF SAID GRIPPING MEANS, SAID STRAP BEING ARRANGED TO PROVIDE A LOOP WHICH DECREASES IN INTERNAL DIMENSION AS THE ENDS OF THE STRAP ARE MOVED APART, A TENSION GAGE SUPPORTED UPON THE FRAME AND ARRANGED FOR CONNECTION WITH THE FIRST OF SAID GRIPPING MEANS, A POWER TRANSMISSION MECHANISM SUPPORTED UPON THE FRAME MEANS AND ARRANGED FOR CONNECTION WITH THE SECOND OF SAID GRIPPING MEANS TO 